As the main by-product of incomplete combustion of hydrocarbon fuel, soot not only has a detrimental effect on the combustion equipment but also harms air quality and human health. The formation of soot is a complex physical and chemical process. It is necessary to decrease the striking differences between the physical evolution and the chemical process of soot generation and combustion. In the past few decades, some scholars have investigated the mechanism of soot generation by spectral diagnostic technology and have had the understanding of soot formation in different generation stages to some extent. By using spectral diagnosis technology, the process of soot generation in the combustion system could be researched more comprehensively, and the molecular composition, fine structure, concentration distribution and other characteristics of soot could also be determined. More importantly, the process could be explained from the changes of soot structure and blackbody radiation intensity in detail. The aim of this study, on the one hand, is to illustrate the research process and developing trend of hydrocarbon flame soot by using spectral diagnosis technology. On the other hand, it is to discuss the problems like the accuracy of the radiation intensity generated during the process of soot generation in flames containing background radiation by the diagnostic tools, LIBS, LII and LIF included. Additionally, the formation mechanism of hydrocarbon flame soot (from precursor generation and growth to particle generation and aggregation, and finally, particle oxidation) is introduced in detail. Meanwhile, it summarized the application of spectral diagnostic methods to detect the properties of soot and the research status of spectral diagnostic techniques on the characterization of soot during combustion, including the volume fraction, reaction temperature and structure characterization of soot based on image processing, and the influence of polycyclic aromatic hydrocarbons, reaction atmosphere and temperature on the formation of soot particles was explored as well. Finally, the future application of spectral diagnostic methods in soot is forecasted. Spectroscopy diagnosis will present a more detailed and accurate study of the chemical reaction mechanism of soot formation in the future. The impact of uneven soot on flame images needs to be reduced, and the development trend of optimizing spectral diagnostic measurement methods to collect and monitor the concentration of multiple gas components in flame simultaneously and the generated soot in real-time. The analysis of spectral diagnostic and image analysis in homogeneous combustion flame soot will provide directions and have crucial scientific significance for promoting clean combustion and heterogeneous flow research.